Respuesta :

x^2 = 360 - (131+105+75)
x^2 = 360 - 311
x^2 = 49
so
x = √49
x = 7

4 inside angles = 360 degrees

131 + 75 + 105 = 311

360 - 311 = 49

x^2 = 49

x = sqrt(49) = 7

x = 7